The Glycobiology Core will provide a resource for all Center members providing expertise and facilities in glycan/glycoprotein engineering and structural analysis of glycans. Approximately half of the molecular mass of HIV gp120 is comprised of N-linked glycans that shield the protein backbone. These glycans impact on vaccine design in three distinct ways. Firstly, the carbohydrates themselves are distinct from typical human glycosylation and can serve as a target for broadly neutralizing antibodies. Secondly, the glycans of gp120 limit or modulate antibody recognition of underlying protein epitopes. Finally, both viral (and immunogen) glycans can interact with host cell lectins and trigger major immunomodulatory signaling pathways. The Glycobiology Core is devoted to supporting Center members in the optimization of these critical parameters for vaccine design.